1-carbamyl-4-heterocyclopiperazines



radicals and/or alkyl- Patented Aug. 22, 1950 UNITED STATES ear Eur OFFICE 1- CARBAMYL-4-HE'TEROCYCIJO- PIPERAZINES Hugh Wendell Stewart, Plainfield, J assignor to American 'Cyanamid. Company, New York, N. Y., a corporation of Maine No Drawing. Application November 12, 1947, Serial No. 785,532

1 The present invention relates to N-heterocyclic piperazines. More particularly it relates to the preparation. of lA-disubstituted piperazines having a group in the l position and a nitrogen containing heterocyclic substituent in the ei-position and to the compoundsso produced.

More specifically the present invention relates to compounds of the following generic formula:

wherein l-Iet represents a 5 or 6 membered heterocyclic radical containing at least one hetero nitrogen atom, and in some cases additional hetero atoms comprising nitrogen, sulfur or oxygen. The group designated Het, for example, may be selected from the group consisting of the pyridyl, pyrimidyl, pyrazyl, thiazolyl and the like or halogen-substituted 'pyridyl, fpyrimidyl and pyrazyl radicals. In the piperazine ring the bond from the nitrogen in the 4-position is to a grouping inthe Het radical. B may be an alkyl radical .of from 1 to 6 carbon atoms.

The compounds of the present invention being IA-substituted piperazines, the latter ring is shown as saturated. However, in addition to the "lxl-substituents, the carbon atomsof thering vniay also be substituted. As shown in the. generic formula above, yi'and yz maybe either hydrogen or a lower alkyl group, particularly the methyl and ethyl radicals. The invention therefore con- :ing'iipoint is very .low', in which casestlie "corn- 6 Claims. ('01. zs o zso) templates 1,4-disubstituted monoand di-alkyl pounds may take the form of an oil. The compounds are,,in general, only slightly soluble in water but readily soluble in the ordinary alkanols, chloroform, ether, and, to varying extent, hydrocarbon solvents such as naphtha. Some of the compounds are sufiiciently basic in character, to form addition salts with acids such as hydrochloric, hydrobromic, sulfuric, citric and the like. Others, however, do not form a readily defined salt. Where formed, the acid addition salts are generally water soluble, and some are even hygroscopic.

Preparation of the new compounds of the present invention may be accomplished in several ways, dependent to a large extent on the nature of the product to be obtained. Some methods are of general application. Others are specificto particular compounds or a group or groups of compounds.

. However, two methods are generally applicable to the preparation 'of these new compounds. Using X to represent the 1 grouping and Y to represent a halogen radical,

these procedures may be represented as follows:

Het

Since l-carbamyl-piperazines may be readily prepared, method (2) above is generally to be.

principally upon the reactivity of the halogen group in the halogen-substituted heterocyclic compound used as starting material. Since bromo heterocyclic compounds possess a more reactive halogen atom than corresponding chloro heterocyclic compounds, and, for example, since 2-chloropyrimidine possesses a much more reactive halogen atom than 2-ch1oropyrazine or 2- bromo-pyridine, reactions involving these compounds may be carried out under quite different conditions.

In general, where z-chloropyrimidine or a compound having a similarly reactive halogen is used as the halogen-substituted heterocyclic compound in method (2) above, a rapid reaction occurs simply by heating under reflux the halogen compound with a l-carbamylpiperazine in a solvent such as ethanol. Usuallythis is done in the presence of an acid-accepting-agent such as an alkali metal carbonate or bicarbonate.

In contrast to this, in order to achieve, in areasonable time, a comparable de ree of completeness in a similar reaction in whichfl chloropyrazine, 2-bromopyridine, or a compound "having a similarly reactive halogen is .utilizedin place of the more reactive halogen compound such as 2-chloropyrimidine, it is necessary forthe reaction to be carried out under-reflux.in, an

inert high-boiling solvent, such as a dichloroe benzene, and in the presence of an acid accepting agent, or in a high-boiling acid-accepting solvent such as quinoline; lutidine, etc.

The .new products Of'ith. present invention .as derived from these reactions mayzbe isolated in a variety of ways, depending-uponthe .reaction medium. In some. cases, where the reaction .is carried out in water-immiscible solvents, the :ex-

:traneous salts present in the reaction mixture are dissolved by the addition of "water in which the product is substantially insoluble. The

product .maythen .be removed. from; thean onaqueous layer by extraction. as.=a .saltithereof with an aqueous solution of. a. saltJorming. acid. The extract may then be treated to separate product from the solvent and the'formerpuri tied. in any suitable manner asiby distillatiomrecrystallization and thelike. Thesmorezsuitable .methcds are demonstrated belowin the illustrative, examples.

When it is desirableand possible to form a salt of the free base, it is only necessary .to treat a solution of the base with the salt-forming acid. An-acid solution may be added toa solution of the base, or, if the acid is a gas, it maybe simply bubbled through the solution. Precipitation of the salt is readily accomplished by evaporation.

In some cases, reduced pressure and/or drying.

agents may be required. This is due to the fact, noted above; that some of the salts are hygroscopic- Some of the salts obtained as well idefined crystals appear to be in a partially hydrated form..

Amongthenew compounds ofthepresent invention may be listed those havingthe general formula set forth above in which I-Iet has the value defined therein. X in the general formula may be quite widely varied and; as noted-abovemay constitute the residue ofanamine-bf-the type,

wherein R has the-values noted above. Typical compounds of the present invention are those represented by the general formula:

is then taken -up'in diethyl ether.

distilled. The product,

wherein Het and R have the values shown in the following table:

Compounds of the present invention exhibit surprisingly varied properties. The compounds -in-' gener-alhave analgesic properties; They-exhibit distinct possibilities as-pharmacologicallyactive compounds for'this purpose: They. are characterizedby lowacute toxicity;

The preparation of typical compounds of the present invention is more ,fully shown in conjunction with -the use of ,lediethylcarbamylpiperazine in the following-examples which are given as illustrative only and not by Way of limitation All parts are byweight. unless otherwise, noted.

EXAMPLE 1 1 diethylcarbamyZ-L (2=pyrazyl)' pipemzz'ne To parts of o-dichlorobenzene are added 92,5,,.parts, of. .1ediethylcarbamylpiperazine, 57

. parts of ,2-chloropyrazineand 84 parts of sodium yellow-oil. This oil,which solidifies-on= standing, melts at -39-43 C. Thelhyd-rochloride, prepared by reacting the base in-ethanolsolution with hydrogen chloride gas, melts with decomposition at 1 33135C.

EXAMPLE 2 1 :diQthyZcarbamyZ-4- [2- (5 -chlor0- pyrimidylll -.pip,ezazz'n'e O 1 art .0 t 1 a oho a jl a t of '1=-diethylcarbamylpiperazine, 84 parts of sodium bicarbonate and 74.5 parts of 2,5-dichloropyrimidine. After the initial exothermic reaction subsides, the reaction mixture is heated under reflux for one-half hour. The resultant inorganic salts are removed by filtration of the hot solution and the salt cake is washed with 158 parts of hot ethanol. The filtrate is combined with the washings, treated with 200 parts of water and cooled. The product, which separates, is isolated by filtration, washed and dried. There is obtained 146 parts of white l-diethylcarbamyl 4 [2 (5 chloropyrimidyD] piperazine. The product is further purified by crystallization from aqueous ethyl alcohol. The pure piperazine compound melts at about 77-'78 C. a

I claim:

1. A l-heterocyclic piperazine of the formula Hetwherein m and ya are selected from hydrogen,

methyl and ethyl, Het is a radical selected from group, and R is selected from the lower alkyl radicals of 1 to 6 carbon atoms.

2. A l-heterocyclic piperazine of the formula 0 R ll/ wherein Het is a radical selected from pyridyl,

pyrimidyl, pyrazyl, and their halogen substituted derivative radicals, the bond from the nitrogen in the piperazine ring to Het being to a piperazine.

6. 1 diethylcarbamyl 4 [2 (5 chloro pyrimidyl) l-piperazine.

HUGH WENDELL STEWART.

N 0 references cited.

Certificate of Correction Patent No. 2,519,715 August 22, 1950 HUGH WEN DELL STEWART It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 44, after the Words such as insert methyl-,;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of November, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant C'ommz'ssioner of Patents. 

1. A 1-HETEROCYCLIC PIPERAZINE OF THE FORMULA 